The most talked about energy pipeline in the world is Keystone XL. It's a conduit to ship oil from Alberta, Canada, through the middle of the United States, into the Texas Gulf Coast for refining. But what makes it so controversial?

On the streets of downtown Houston this fall, there was a protest over a pipeline that isn't built yet.

"That pipeline is going to bring some of the dirtiest stuff on Earth across the United States, down here to Houston where it can be refined and shipped to Asia and burned. There's not a drop of oil that's going to be brought into America unless it spills from this pipeline," Keystone XL Pipeline opponent Becky Bond said.

Thirteen people were arrested, arguing the much-talked-about Keystone XL pipeline is dangerous, bad for the environment and will not inch the U.S. towards North American energy independence.

As much as environmentalists in the United States have their concerns about Keystone XL and what it would do in the middle of the country, there are even greater concerns in Alberta, Canada.

That is because of the oil sands -- the expansive area where oil is pulled from the ground in a traditional way, through steaming or by mining it from the heavy Alberta sand. It is a toxic process. And the more pipeline there is to carry the oil, the more energy companies will expand their already growing footprint in those oil sands.

"So I think there is such a thing as there being too much. And I think right now, Canadians are wrestling with that question. How much is too much?" said Jennifer Grant with the Pembina Institute, an environmental think tank in Calgary.

The Pembina Institute suggests the resulting development because of Keystone XL would add the carbon equivalent of four million cars to the road.

"It's premature to talk about approving the Keystone XL, or any other pipeline for that matter, right now until we've been able to reconcile some of the issues we have on the ground as it relates to regional impact," Grant said.

The regional impact though could mean lots and lots of money. Much as the fracking boom in Texas has led to an economic Renaissance, the expanded exploitation of the oil sands has meant jobs and growth for communities through Alberta. TransCanada is already expanding its Keystone distribution hub in Hardisty, Alberta, to accommodate more oil coming its way whether or not XL gets approved.

There is additional space ready at the company's pipeline control center in Calgary, ready to accommodate potential growth.

And if Keystone XL is built from Hardisty to Steel City, Nebraska, it could mean jobs all along the pipeline's route to here in southeast Texas.

"Fifteen million barrels of oil is used by Americans a day; eight million of that is imported. So the Gulf Coast, currently right now, will be able to displace a lot of that imported oil that's coming in," said Jacquelynn Benson with TransCanada.

Cruz has met with TransCanada, the company wanting to build the pipeline, and says it's about jobs, national security, taxes, and believe it or not, the environment because if not the pipeline, the oil comes to southeast Texas refineries in tankers.

"Even if you are a Birkenstock-wearing, bearded Greenpeace member, you should love the Keystone pipeline," Cruz said.

There are those who do love the idea and those, like the men and women we found protesting here in Houston, who do not. That's part of the reason it's taken the White House so long to make a decision one way or the other.